Effluent treatment system

ABSTRACT

A treatment system for liquid or liquid and solid effluent. The system is enclosed within a pipe, duct (10) or trench and comprises one or more sloping filter beds (12, 13, 14) with a population of effluent decomposing organisms such as earthworms and mothflies, and an overlying air space. The aqueous media effluent inlet (11) is located above the uppermost filter bed at an upper end and the solid waste input inlet (31), when included, is located downstream of the aqueous media inlet so that the aqueous media flows through and around the solid waste material. A filtrate outlet (28) is located downstream of the flow through the system and manual or conveyor means are provided for solids removal.

BACKGROUND OF THE INVENTION

THIS invention relates to the treatment of aqueous media and solidorganic material to remove constituents which are hazardous or toxic tohumans or the environment.

Conveyancing pipes or ducts used in conventional aqueous media treatmentsystems are not specifically engineered to effect any treatment, andconsequently very little effective treatment occurs inside most pipesleading to or from treatment systems despite the fact that the pipescontribute substantially to the cost of the overall waste treatmentsystem. In centralised sewerage treatment schemes the collection systemcan cost as much as the treatment plant to install. In a typical on-sitetreatment system for a single detached dwelling, 10 to 20 meters of 100mm diameter pipework, or equivalent, leads to the treatment chamber, anda further 20 to 30 meters leads from the treatment chamber to thedisposal/re-use area. Within the disposal area another 20 to 40 metersof pipe is commonly used in addition to trench support material,aggregate liners, and the like. Typically the treatment chamber isdesigned to be relatively large in order to provide sufficient retentiontime for treatment. Both aerobic and anaerobic treatment systems aretypically bulky and deep in order to provide sufficient retention timefor aqueous media treatment.

In sewered allotments there is much more than the equivalent of 60meters of 100 mm diameter pipe, when a share of the common reticulationnetwork is apportioned to each connection serviced

Aqueous media pipes have much to recommend them as aerobic treatmentsystems. They have a vented air space available above the aqueous medialevel most of the time, are usually out of sight, and are ofteninstalled in the ground or in buildings where the extremes oftemperature are moderated.

A method of using a bed of decomposed and decomposing solid organicwaste material to filter aqueous media is known and used commercially.The method uses a relatively deep bed thickness to effect thefiltration. It also employs a technique where the filter bed is more orless evenly loaded. This results in some practical constraints.

1. The outlet drain for the treated water is considerably lower than theaqueous media inlet pipe. This often results in a need to pump theeffluent where the land is fairly flat or where the water table is high.

2. The bio-solids removed from the system are continuallyrecontaminated, and pathogens are not deactivated before removal.

3. Opportunity exists during heavy loading periods for the bed to betemporarily inundated since the aqueous media cannot flow anywhere else.This results in a less diverse community of breakdown organisms beingable to survive under these circumstances.

4. A treatment chamber with horizontally arranged long axis has a highersurface area than a vertically arranged treatment chamber.

OBJECT OF THE INVENTION

One object of the invention is to avoid the use of pipes whose solefunction is to convey effluent to treatment systems.

Another object of the invention is to overcome the problems of existingeffluent treatment systems as mentioned above.

SUMMARY OF THE INVENTION

According to the present invention there is provided an enclosedeffluent treatment system incorporating a sloping filter bed with aliving population of effluent decomposing organisms and an overlying airspace, an aqueous effluent media inlet above the filter bed at an upperend thereof, a filtered aqueous media outlet and, optionally, a solidwaste input region downstream of the aqueous media inlet and means forsolids removal.

The invention thus covers both an aqueous media purification system andan aqueous media and solid organic waste treatment system. The term"effluent" used throughout the specification can refer to one or otherof these input streams.

DETAILED DESCRIPTION OF THE INVENTION

Where more than one filter bed is configured, the beds are preferablystacked in vertical layers. Preferably there is a ventilated spacebetween these beds.

The filter bed(s) is(are) enclosed to prevent contamination of theenvironment by the waste material or potential vectors of disease. Theenclosure can typically comprise a pipe, duct or trench. A duct or pipetypically includes a longitudinal lower inner surface with the filterbed arranged above that surface and extending the length of the duct orpipe.

A solid organic waste input chute may be arranged downstream of theaqueous media inlet in such a way that the aqueous media is caused toflow through and around the solid organic waste material added throughthe input chute.

In one form of the invention, one of the filter beds functions as aconveyor belt to discharge decomposed organic material at a downstreamend of the treatment system. In another form of the invention,decomposed organic material is transmitted through the or each filterbed and is removed from a downstream end of the treatment system byfiltrate flow.

A means of collecting the filtrate which filters through the filterbed/s may be arranged below the lowest filter bed, or if the filtrate isnot required, then the filtrate may infiltrate directly into the soilbelow the lowest filter bed.

The build up of decomposed organic matter, non-biodegradable solids orslime growth from the surface of the filter bed(s) is suitably carriedout as required.

The treatment system can be mounted free standing or suspended below afloor, buried under a floor slab or buried in the ground, or have anyother suitable configuration for the particular treatment being carriedout.

A flow of aqueous media to be treated enters the system via an aqueousmedia pipe or series of pipes and is caused to pass along and throughthe filter bed(s).

If the system is designed to treat solid organic waste material then theorganic waste material is either placed directly in the system in a moreor less unprocessed form, for instance from a food waste scrap bucket orwastepaper bin or the like, through the solid waste entry chute locateddownstream of the aqueous media entry pipe, or it may be processedthrough a waste grinder and so enter the system as a constituent of theaqueous media. The input flow of aqueous media washes and deposits thesolid organic waste material along the surface of the filter bed. Theliquid portion of the aqueous media infiltrates into the filter materialwhich forms the bed and can be either collected for some reuse purposeor discharged onto a second filter bed or into the soil. The solidorganic waste material is retained in and on the filter bed.

The size of the air space required above the filter bed is determined bythe largest particle size of the solid organic material added to thefilter bed.

The waste matter added to the filter bed decomposes rapidly in thepresence of the moisture and air contacting the organic fragments leftbehind as the liquid portion passes through the filter bed.

Air above and through the pore spaces in the filter bed, moisture fromthe aqueous media, and energy and nutrients in the solid organic matteror dissolved and suspended in the aqueous media, provide a very goodenvironment for organic decay by endemic microorganisms in the aqueousmedia, and introduced or ubiquitous invertebrates and microbes living inand on the decomposing and decomposed organic material.

One form of the present invention uses actively decomposing solid wasteand fully composted waste as a physical and biological filter medium forwaste water.

Solid putrescible wastes adjacent the entry will act as a media forbiofilm growth as aqueous media is applied. Large discrete wasteparticles are continually added and continually digested by theorganisms and eroded by aqueous media so that they are constantlybreaking up into smaller and smaller particles ultimately forming stablehumic colloids and dissolved humic compounds. The wetting and dryingcycles combined with the extrusion of discrete worm casts and insect andmite frass create a relatively stable compost crumb structure within thecompost bed formed from the decomposed solids in the enclosure.

The movement of worms, beetles, mites, collembola and insect larvaethroughout the compost aerates the compost medium and prevents theinternal drainage of the bed from blocking. Thus the compost bed comesto act like a well drained soil bed with a huge wetted surface area foroxygen exchange. Air is drawn into the compost bed every time wastewater is pulsed onto it by normal sporadic household usage. Partialinundation of the compost bed surface occurs with normal usage. Wherethis happens, waste water infiltrates rapidly through the biopores andacts like a hydraulic piston to draw fresh air into these pore spaces.

Unlike aquatic treatment systems, the present invention quickly filtersout the larger solid wastes (which have a high oxygen demand) onto thesurface of the compost bed where they are surrounded by air. Since airis 22% oxygen, and has much faster diffusion rates than water, muchhigher biological loadings can be treated this way.

If the solid organic waste material input is large the solid organicfragments themselves form a large surface area media which acts as atrickling filter aggregate when wetted by the aqueous media flowing overand around such fragments.

The compost produced by the decay of the solid organic waste materialwhich accumulate on the surface of the filter bed acts as a fine aerobicfilter medium and adsorptive treatment contact surface.

The enclosure is constructed so that the aqueous media is caused to flowlongitudinally along the sloping surface of the filter bed away from theinput end of the enclosure.

The surface of the filter bed and any organic matter build-up isprevented from blocking by the action of worms, mothflies, mites,collembola and other soil organisms.

The infiltration rate and surface area exposed to the air can beincreased by adding a bulking agent such as polystyrene beads orgranules to the surface of the filter bed.

The fine compost like organic media provides a habitat for invertebratesand microbes feeding on the organic material.

The compost bed acts as a self regenerating filter medium for the wastewater and can also be used to create a suitable habitat to supportorganisms which decompose solid organic wastes into stable humiccompounds.

The waste water may flow into the pipe or duct at one or more pointsalong the pipe or duct.

The waste water will infiltrate into the compost bed over variousdistances along the length of the compost bed depending on the inputflow rate, duration, and waste water infiltration rate. A high flow rateover an extended period of time will infiltrate for the greatestdistance along the compost bed. For any particular situation, it ispreferred that the compost bed be long enough so that a far end portionof the bed will be only wetted occasionally during peak hydraulicloading events.

The infiltration rate will vary along the length of the compost bedaccording to the permeability of the combined solid waste layer, compostbed and compost bed support medium. In the frequently wetted high flowzone a zoogloeal slime of microorganisms and fine particulate solids cancoat the surface of the compost bed and particulate solid wastes andlead to a lower permeability in the influent high loading zone than thatat the limit of infiltration. This desirable phenomenon will also beobserved laterally across the surface of the filter bed if the innersurface is curved so that the lowest point is away from the edges of thebed.

Solid wastes are distributed over the surface by the flowing wastewater. The pattern of distribution is related to the waste watervelocity, hydraulic flow and infiltration pattern along the compost bedas well as the solids particle size, shape, buoyancy, stickiness,mechanical strength, decomposition rate and errodability. Erosion of thesurface of the compost/solid waste deposits is related to the wastewater velocity as well as the surface characteristics. Erosion ingeneral moves smaller crumbs or particles but movement of largerfragments can also occur where large aqueous media flow rates can carrylarge buoyant solids along the filter bed to the point where thefriction between the solid particle and the filter bed is greater thanthe frictional drag on the solid particle produced by flowing aqueousmedia.

Typically, the shape and length of the enclosure and filter bed are soarranged, and organisms therein are so managed, that the rate of compostremoved from the enclosure is approximately equal to the amount ofcompost produced.

Bio-solids are produced by the system which can be harvested asstructured compost like material. Harvesting should preferably occurafter a period of low hydraulic inputs to the system.

Filtered effluent is also discharged from below the lowest filter bed.It may be allowed to infiltrate into the soil without further treatmentor it may be collected and reused for some specific purpose. Wheresecondary filter beds are employed the filtrate can be of sufficientquality to safely reuse for toilet flushing, garden watering, and thelike.

The solid organic material is progressively moved from the entry pointto the discharge end as it decomposes by various methods as describedbelow.

Biological activity can also result in the mass movement of solids. Inparticular the activity of composting worms and various species ofinsects (such as mothfly larvae) produces small friable castings andfrass which are usually deposited in such a way as to level out thelongitudinal surface topography of the compost bed. Because of apreference of worms to cast in the drier edge zones, the lateral curveof the bed surface is maintained. This activity decreases the bulkdensity of the compost bed surface and also increases the infiltrationrate. The combined effect is to increase the errodability of the surfaceduring high surface flow rates.

The biological activity will stabilise in time to reflect the complexinteraction of various critical gradients such as moisture content, foodavailability, oxygen supply and temperature. Population gradients whichrelate to each particular organism's ability to competitively exploit aparticular habitat niche will be evident.

In time selective pressure will result in the evolution of moreprecisely adapted organisms from all the species represented, which canexploit hotter, wetter or lower oxygen zones more efficiently.

Blockage of the surface flow could occur if particulate build up on thefilter bed occurs to the point where peak flow is dammed within the ductand does not disperse the build-up of solids over a sufficient area toallow the maintenance of a dynamic equilibrium between deposition anddecomposition rates.

Biological activity maintains the height of the compost/solid wastesurfaces in a dynamic equilibrium. This means that solids are washeddown the length of the compost bed and moved downwards through thesolids permeable compost bed through washing and biological activity atthe same rate as they are deposited. Internal blockages can occur if thebed support material has a pore size too small to transmit very finesolids and these accumulate within the bed and slow the infiltrationrate down to the point where the hydraulic application ratesconsistently exceed filter bed infiltration rates. To avoid this the bedcan be configured to be permeable to very fine colloidal solids or tolarger particle sizes by manipulating the pore size of the bed material.

In practice where a reasonably high solid organic waste materialapplication rate applies, a medium with a 0.5 mm to 1 mm pore size hasbeen shown to maintain an effective dynamic compost layer equilibrium inthe upper layer.

If faster solid throughput rates are required for very high solidorganic waste material application rate systems, the pore size would beincreased appropriately.

Where the aqueous media is relatively clean, the media used in thefilter bed can be very fine and granular and should be soil and litterorganisms such as earth worms and/or mothflies to consume the growth ofmicroorganisms which grow on and are filtered out by the media. Finesand, powdered activated carbon or other suitable granular materialusually with an effective particle size of 0.1 mm or less are twopreferred media if the filtrate is to be recycled for flushing or asimilar use. Where the aqueous media application rate exceeds theinfiltration rate there will be a surface flow. This can be used toadvantage to transport the fine composted solid organic waste materialto the lower end of the treatment system where it can be convenientlyaccessed for removal.

The size of the pipe or duct required will depend on the solids andhydraulic loading rates applied. High solids loadings will requiresteeper gradients and hence higher waste water flow velocities toproduce a larger surface area and hence infiltration zone. The slope ofthe pipe or duct should be such that the deposition of solid materialsis spread evenly along a sufficiently long length of the compost bed toallow the decomposition and compost removal rate to equal the raw solidsdeposition rate.

A range of filter bed gradients can be used depending on the solidapplication rate, size of the solids applied and aqueous mediaapplication rates. The slope of the filter bed should be designed toachieve more even solids distribution over the surface of the filterbed.

If the treatment duct gradient is high, transverse baffles perpendicularto the waste water flow direction may be required to prevent the compostbed from eroding too quickly and allowing unfiltered waste water to passthrough the supporting material openings. Because the infiltration rateand errodability of the solid organic waste material and bed medium willvary along the length of the treatment duct, the gradient of the filterbed may also need to be adjusted along the length of the treatment ductfor some applications.

Where the bed is to be mechanically progressed it is preferable todesign the system so that the peak flow infiltration zone stops wellshort of the end of the compost bed so as to allow a compost maturationzone which is not re-contaminated by pathogens from the waste waterprior to harvesting.

In a low solids loading situation passive transport of solids by wastewater movement and biological activity could be used in conjunction withperiodic servicing of the bed to remove non-compostable and slowlydegradable composted solids. Such servicing could be effected by a jetor series of water jets directed onto the compost bed in such a way asto flush off surface build-up of compost and non-compostable solids.

These fine composted solids could be filtered out of the filtrate by afiltration material located at the filtrate discharge point/s orfiltered out by a second finer, in duct filter bed medium, positioned soas to accept the primary compost bed filtrate and the organic solidswashed through the primary filter bed.

In the case of high solids input rates and or the addition of largenon-compostable solids such as plastics, glass or metals, it may benecessary to form the compost bed to be movable so as to discharge thebuild up of solid material at some point or points along the length ofthe container. Ideally the discharge of solid material would only occurafter a sufficient interval has elapsed from when fresh wastes were lastdeposited to allow for their complete decomposition to pathogen freestable humus.

The internal volume within the container, duct or pipe must be largeenough to prevent the occlusion of the pipe given a specific solidorganic waste material movement rate and solids deposition rate. Themovement of the solids in a high solids loading application may beeffected by forming the compost bed support medium into an endlessconveyor belt and causing it to rotate slowly or in pulses toward thecompost discharge point(s). A motor or mechanism driven by the combinedwater flow into the building serviced could be used to provide aregulated movement related to aqueous media flow rates.

The enclosure, pipe or ducting employed to hold compost is preferably sosized and dimensioned as to cater for the particular waste loadings forthe environment of use.

Preferably, the filter bed comprises a non-biodegradable support media,such as durable fibre wadding, durable thermo-plastic textile or lineardrainage ducting, extending along the enclosure dividing the enclosureinto upper and lower regions and being adapted to pass aqueous media andfinely divided organic material, the upper region being adapted to holdpartially decomposed organic material and compost, and the enclosurehaving a cross-section and length, and supporting sufficient filtrationmedia so that aqueous media entering the enclosure is absorbed in thelength of compost in the enclosure. The enclosure can include a meansfor dislodging or washing off undesirable surface build up from thefilter bed. In one example, the dislodging or washing off meanscomprises a plurality of water jets spaced along the enclosure andcontrol means to operate the jets at predetermined times.

In another embodiment, a secondary filter bed can be employed beneaththe primary filter bed. This enables removal of fine particulate organicmaterial which wash through the coarse primary filter bed media.

In this application of the present invention to in-duct or in-pipetreatment a long thin compost bed is formed on a fixed or movablesupport medium, typically a non-biodegradable thermo-plastic fibrousmaterial within the duct or pipe.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an enclosed effluent treatmentsystem according to one aspect of the present invention;

FIG. 2 is an enlarged end-sectional view of the system of FIG. 1;

FIG. 3 is an enlarged partial view of the left end section illustratedin FIG. 1;

FIG. 4 is an enlarged partial view of the right end section illustratedin FIG. 1; and

FIG. 5 is an end-sectional view of an enclosed effluent treatment systemaccording to another aspect of the present invention.

In all of the drawings, like reference numerals refer to like parts.

DESCRIPTION OF PREFERRED EMBODIMENTS EXAMPLE 1

This example concerns a duct treatment system for treating wastewaterand solid organic waste so as to recover and store the filtrate forreuse in toilet flushing or like grey water applications.

Referring to FIGS. 1 to 4, the treatment system comprises an extrudedplastic duct 10 with appropriate reinforcement ribbing, as the treatmentenclosure. The enclosure is mounted on an inclination of approximately1:100 with the higher end containing the inlet 11 for wastewater andsolid organic waste material.

Three filter beds 12, 13, 14 are supported by three drainage supportelements 15, 16, 17 which are slidably removable in grooves 18, 19, 20located on the sides of the duct. Sides are provided on the drainagesupport elements to contain the filter media placed or formed thereonand so as to enable the entire filter beds and support elements to beclearly removed for servicing or media replacement.

The drainage support element beds are provided with material covers bothabove and below the horizontal surfaces. The uppermost drainage supportelement 15 is provided on its upper surface with a knitted thermoplasticfibre material 21 having a hole size of approximately 1 mm. The lowersurface of the drainage support element 15 has a geotextile fabric 22adhered thereto. A similar geotextile fabric 23, 24 is fitted to theother two support elements, over their upper and lower surfaces.

Ventilation spaces 25, 26, 27 are provided at each end of the drainagesupport elements to enable excess wastewater to bypass in high loadingtimes. At the downstream end there is provided a drainage passageway toenable this water to bypass to the secondary and tertiary filter beds13, 14.

A solids input chute 31 is located on the downward slope spaced from thewastewater inlet 11 and a filtrate outlet 28 is located at the lowermostregion of the enclosure.

In use, wastewater enters by way of inlet 11 and waste solids by way ofchute 31. The chute is arranged so as to cause the wastewater to flowthrough and around the waste solids on the primary filter bed 12. Theprimary filter bed is designed to enable fine composted material to washthrough the bed assisted by the action of the organisms in the bed. Oncethrough this layer the fine compost accumulates over the geotextilelayer and forms a second thin filtration bed of compost. The compost inthis layer is only slightly heavier than water and is easily eroded andcarried down stream and discharged through the drain hole 20. Oncedeposited onto the second filter bed 13 the fine suspended solid organicmaterial is easily removed during low water usage periods by removing aduct end cover and sliding out the filter bed support element.

The upper filter bed 12 can be made to work more efficiently by addingpolystyrene foam beads or some similar bulking material 30 to thesurface of the filter bed.

The filtrate exiting from the outlet 28 is suitable for collection andused in recovered water applications such as toilet flushing, landscapeirrigation and such like.

EXAMPLE 2

In this example there is no requirement to reuse the filtrate. In thiscase a slotted ribbed pipe 50 of at least 150 mm is wrapped ingeotextile fabric 51 and mounted on a bed of fine sand 52 and backfilledwith 20 mm rock aggregate or similar. The lumen of the pipe has aremovable element 53 of slotted drainage pipe which has a spacer 54under it and a thermoplastic knitted mesh fabric 55 with a hole size ofapproximately 1 mm. The pipe may be continuously formed between thewaste water source and a biosolids collection pit, or may connectseveral point sources and have biosolids collection pits at appropriateintervals. The effluent discharged through slots 56 in the pipeinfiltrates into the soil under and surrounding the pipe. The removableelement 53 in the lumen of the pipe enables servicing of the filter bedat long intervals to remove any accumulated non-compostable solids.

I claim:
 1. An enclosed effluent treatment system comprising a slopingfilter bed with a living population of effluent decomposinginvertebrates and microbes and an overlying air space, an aqueous mediaeffluent inlet above the filter bed at an upper end thereof, a filteredaqueous media outlet, a solid waste input region downstream of theaqueous media inlet and means for solids removal.
 2. A treatment systemas claimed in claim 1, wherein the filter bed comprises a plurality offilter beds stacked in vertical layers.
 3. A treatment system as claimedin claim 1 or claim 2, wherein the filter bed(s) is(are) enclosed withina duct, pipe or trench.
 4. A treatment system as claimed in claim 1 orclaim 2, wherein the filter bed(s) is(are) enclosed within a duct andis(are) removable through the ends of the duct.
 5. A treatment system asclaimed in claim 1 or claim 2, wherein the solid waste input regioncomprises a chute which allows aqueous media to flow through and aroundsolid waste material added by way of the chute.
 6. A treatment system asclaimed in claim 1 or claim 2, wherein the uppermost filter bed ispartially comprised of a compost bed.
 7. A treatment system as claimedin claim 1 or claim 2, wherein the or at least one of the filter beds iscomprised of a granular material which is populated with earthwormsand/or mothflies.
 8. A treatment system as claimed in claim 1 or claim2, wherein the filter bed(s) is(are) enclosed within a trench and thefiltered aqueous media outlet is the ground forming the base of thetrench.
 9. A treatment system as claimed in claim 1 or claim 2, whereina bulking material is added to the surface of the or each filter bed toincrease the aerobic capacity and infiltration rate.
 10. A treatmentsystem as claimed in claim 1 or claim 2, wherein the filter bed(s) is(are) enclosed within a duct constructed from ribbed thermo-plastic withlongitudinal grooves formed in the sides to support a removablethermo-plastic drainage and support element.
 11. A treatment system asclaimed in claim 1 or claim 2, wherein the effluent decomposingorganisms are selected from the group consisting of earthworms, beetles,mites, and insect larvae.
 12. An enclosed effluent treatment systemcomprising a sloping filter bed within a duct constructed from ribbedthermoplastic having longitudinal grooves formed in the sides to supporta removable thermoplastic drainage and support element, said filter bedhaving a living population of effluent decomposing invertebrates andmicrobes and an overlying air space, an aqueous media effluent inletabove the filter bed at an upper end thereof, a filtered aqueous mediaoutlet and a solid waste input region downstream of the aqueous mediainlet and means for solids removal.
 13. A treatment system as claimed inclaim 12, wherein the filter bed comprises a plurality of filter bedsstacked in vertical layers.
 14. A method of treating solid wasteeffluent and aqueous media effluent, said method comprising:introducingsaid aqueous media effluent into an aqueous media effluent inlet;introducing said solid waste effluent into a solid waste input regiondownstream of the aqueous media inlet; flowing said aqueous mediaeffluent and solid waste effluent onto a sloping filter bed with aliving population of effluent-decomposing invertebrates and microbes andan overlying air space; filtering and decomposing said aqueous mediaeffluent and solid waste effluent through said filter; and removingresulting filtered and decomposed aqueous media and solids.
 15. Themethod of claim 14, wherein the sloping filter bed and overlying airspace are in an enclosed structure.
 16. The method of claim 14, whereinthe filter bed comprises a plurality of filter beds stacked in verticallayers, and wherein the filtering and decomposing step comprisestransmitting partially filtered and decomposed aqueous media effluentand solid waste effluent from one filter bed to another.